Photocatalytic surface systems

Abstract

The Invention describes integration of photocatalytic materials into composite surfaces in order to achieve antimicrobial properties. Aspects of the invention include types of photocatalytic materials and methods to achieve long lifetimes, high durability and mechanical robustness, for application to medical and sanitary uses, among others. In particular, the invention describes production of photocatalytic islands on a porous support substrate, and various methods to prevent full contact of a matrix material with the photocatalytic islands on the porous support substrate when forming the photocatalytic composite. Reducing the area of contact between the matrix material and the photocatalytic material improves the lifetime of the photocatalytic materials employed in the photocatalytic composite.

What is claimed is: 
     
       1. A photocatalytic surface system, comprising a UV-A or visible light activated titania-based photocatalytic material in contact with a matrix material, wherein the photocatalytic material consists of a mixture of photocatalytic surfaces and non-photocatalytic surfaces, there being a plurality of contact interfaces between the matrix material and the photocatalytic material, wherein less than 90 percent areal density of each of the plurality of contact interfaces is between the matrix material and a photocatalytic surface of the photocatalytic material, the remainder of the contact interface being between the matrix material and a non-photocatalytic surface of the photocatalytic material. 
     
     
       2. The photocatalytic surface system of  claim 1 , wherein the photocatalytic material is a colloidal photocatalytic nanocrystal capped with non-photocatalytic solubilizing ligands. 
     
     
       3. The photocatalytic material of  claim 2 , wherein the solubilizing ligand is selected from the group consisting of alkoxysilanes, phosphonic acids, carboxylic acids, alcohols, and sulfonic acids. 
     
     
       4. The photocatalytic material of  claim 2 , wherein the colloidal photocatalytic nanocrystals are 2-15 nm in diameter. 
     
     
       5. The photocatalytic surface system of  claim 1 , wherein the photocatalytic material comprises a monolithic composite photocatalyst support having pores, the pores having photocatalytic surfaces dispersed within them, the photocatalytic surfaces covering no more than 90 percent areal density of the surface of the monolithic composite photocatalyst support, the monolithic composite photocatalyst support being formed of a non-photocatalytic material, together forming a monolithic composite photocatalyst. 
     
     
       6. The photocatalytic surface system of  claim 5 , wherein the monolithic composite photocatalyst comprises photocatalytic particles forming the photocatalytic surfaces, wherein the photocatalytic particles incorporate a core-shell geometry, wherein the shell layer is non-photocatalytic, further wherein the shell layer has been at least partially removed at the matrix surface to enable greater antimicrobial efficacy. 
     
     
       7. The photocatalytic surface system of  claim 6 , wherein the shell layer is comprised of silica, alumina, zirconia, hafnia, Si x N y , Si—C—O—N, or silicon. 
     
     
       8. The photocatalytic surface system of  claim 5 , wherein the external surface of the monolithic composite photocatalyst is greater than 50% free of active photocatalyst nanoparticles by percent areal density, wherein photocatalyst is present in the interior pores of the monolithic composite photocatalyst, wherein a portion of the monolithic composite photocatalyst has been at least partially removed at the matrix surface to enable greater antimicrobial efficacy. 
     
     
       9. The photocatalytic surface system of  claim 1 , wherein the photocatalytic material is bulk titania particles coated with a non-photocatalytic shell layer, wherein the shell layer has been at least partially removed above the matrix surface to enable greater antimicrobial efficacy. 
     
     
       10. The surface system of  claim 9 , wherein the shell layer is comprised of silica, alumina, zirconia, hafnia, Si x N y , Si—C—O—N, or silicon. 
     
     
       11. The photocatalytic surface system of  claim 1 , wherein the matrix is comprised of polyurethanes, epoxies or silicones. 
     
     
       12. The photocatalytic surface system of  claim 11 , wherein the matrix contains inorganic nanocrystals, particles or fibers that modify the mechanical properties of the matrix, thereby increasing the resistance of the matrix to mechanical wear. 
     
     
       13. The photocatalytic surface system of  claim 1 , wherein the matrix is comprised of silicon oxide, aluminum oxide, titanium oxide, or refractory oxide forming precursors. 
     
     
       14. A method of manufacturing the photocatalytic surface system of  claim 1 , the method comprising: mixing the photocatalytic material into a paste or liquid thereby dispersing the photocatalytic material in the paste or liquid, dispensing the paste or liquid in a controlled pattern, hardening the paste or liquid to form a solid having a defined shape based on the controlled pattern, thereby suspending the photocatalytic material in the matrix material, exposing at least a portion of the photocatalytic material at a surface of the matrix thereby forming a photocatalytic surface system, and exposing the photocatalytic surface system to UV-A or visible light, thereby stimulating photocatalytic activity. 
     
     
       15. A liquid cleaning agent for cleaning a solid surface, comprising the photocatalytic surface system of  claim 1 , comprising the UV-A or visible light activated titania-based photocatalytic material in contact with a matrix material, the photocatalytic surface system formed into particles, that provides photocatalytic enhancing species to the surface. 
     
     
       16. The liquid cleaning agent of  claim 15 , wherein the liquid cleaning agent is applied by cloths, fibrous implements, mops, sprays, jets, misters or nebulizers. 
     
     
       17. The liquid cleaning agent of  claim 15 , wherein the photocatalytic enhancing species enable Fenton or photo-Fenton reactions. 
     
     
       18. The liquid cleaning agent of  claim 15 , wherein the photocatalytic enhancing species includes Fe. 
     
     
       19. The liquid cleaning agent of  claim 15 , wherein the cleaning agent combines photocatalytic enhancing species and halide containing species. 
     
     
       20. The liquid cleaning agent of  claim 15 , wherein the solid surface contains photocatalytic antimicrobial materials.